JP 2012-130108A describes a vehicle in which a lead storage battery and a lithium ion battery are installed. The lead storage battery is directly connected to an alternator, a starter, and a first electric load. This lead storage battery is also connected to a second electric load via a bidirectional semiconductor switch. The lithium ion battery is connected to the second electric load via a Li (lithium) battery relay.
In JP 2012-130108A, the charge rates of the lead storage battery and the lithium ion battery are calculated, and the semiconductor switch and the Li battery relay are controlled based on conditions that utilize the charge rates and the like.
For example, in JP 2012-130108A, when a ground fault occurs between the lead storage battery and the semiconductor switch, the lithium ion battery can be cut off from the ground fault by switching off the semiconductor switch. Accordingly, the lithium ion battery can supply power to the second electric load. However, in JP 2012-130108A, a single ECU (Electronic Control Unit) switches off the semiconductor switch. Therefore if some sort of problem occurs in this ECU, the semiconductor switch cannot be switched off, and the lithium ion battery cannot be cut off from the ground fault.
In view of this, an object of the present invention is to provide an on-vehicle power source switch apparatus that can reliably switch off a switch that is provided between two power storage devices when a ground fault occurs.